[PATCH] vect: Do not use partial vectors when emulating vectors [PR116351].

[Robin Dapp]

Hi,

in PR116351 we try to vectorize with -march=...zve32x which does not
have 64-bit vector element sizes, don't find a proper mode and end up
using word_mode = DImode.

vect_verify_loop_lens calls get_len_load_store_mode which asserts
VECTOR_MODE_P (vecmode) so DImode will cause an ICE.

In check_load_store_for_partial_vectors we disable partial vectors
when emulating vectors so this patch does the same in tree-vect-loop.cc
before vect_verify_loop_lens is called.

Is this the correct thing to do or should we have taken another
turn somewhere else?

Bootstrapped and regtested on x86, aarch64, and power10.
Regtested on rv64gcv_zvl512b.

Regards
 Robin

        PR target/116351

gcc/ChangeLog:

        * tree-vect-loop.cc: Disable partial vectors for emulated
        vectors.

gcc/testsuite/ChangeLog:

        * gcc.target/riscv/rvv/autovec/pr116351.c: New test.
---
 .../gcc.target/riscv/rvv/autovec/pr116351.c       | 15 +++++++++++++++
 gcc/tree-vect-loop.cc                             | 10 ++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116351.c

diff --git a/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116351.c 
b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116351.c
new file mode 100644
index 00000000000..ed1b985d8fa
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116351.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -march=rv64imd_zve32x -mrvv-vector-bits=zvl" } */
+
+int a, b, c;
+short d, e, f;
+long (g) (long h) { return h; }
+
+void i ()
+{
+  for (; b; ++b)
+    {
+      f = 5 >> a ? d : d << a;
+      e &= c | g (f);
+    }
+}
diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
index 4f401cd2d0c..2cf5a05b70c 100644
--- a/gcc/tree-vect-loop.cc
+++ b/gcc/tree-vect-loop.cc
@@ -3021,6 +3021,16 @@ start_over:
       LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
     }
 
+  if (LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo)
+      && !VECTOR_MODE_P (loop_vinfo->vector_mode))
+    {
+      if (dump_enabled_p ())
+       dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
+                        "can't operate on partial vectors when emulating"
+                        " vector operations.\n");
+      LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo) = false;
+    }
+
   /* If we still have the option of using partial vectors,
      check whether we can generate the necessary loop controls.  */
   if (LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo))
-- 
2.47.1